Several techniques have been developed for the insertion of a catheter into a patient's blood vessel. On such technique is known as the Seldinger technique. The Seldinger technique involves the use of a needle which is initially advanced into an artery at a preferred angle of approximately 30 to 45 degrees. The puncture of the artery is confirmed by the presence of blood in the needle. Next, a flexible J-spring guidewire is inserted through the needle for approximately 15 to 20 cm. The needle is then withdrawn over the guidewire while pressure is applied to the artery to prevent the formation of a hematoma at the incision site. The guidewire is then cleaned with sterile saline and a multipurpose catheter is inserted over the guidewire until the catheter reaches the desired initial location. The guidewire is then removed from the inside of the catheter and the catheter is flushed to remove any thrombus material which may have been picked up as the catheter was inserted into the artery over the guidewire. Finally, the catheter is advanced to a final location such as in the ascending aorta.
In another catheter insertion technique, an introducer needle is inserted through a flexible cannula so that the needle point extends beyond the distal end of the cannula and so that the hub of the introducer needle engages the hub of the cannula. In this technique, the introducer needle and cannula are advanced through the skin of the patient so that the bevel on the distal end of the introducer needle pierces the patient's blood vessel at an angle of approximately 30 to 45 degrees. Once the introducer needle pierces the patient's blood vessel, the introducer needle is withdrawn and the cannula is advanced into the patient's blood vessel. Next, a flexible guidewire is inserted into the patient's blood vessel through the cannula. The cannula is then removed and a catheter is inserted into the patient's blood vessel over the guidewire. Finally, the guidewire is removed and the catheter is flushed to remove any thrombus material from the catheter.
Normally, during this procedure, the nurse must initially determine that the patient's blood vessel has been properly pierced and then while pressing on the patient's blood vessel to prevent the formation of a hematoma at the incision site, the nurse must single handedly separate the needle hub from the hub. During the insertion and removal of the introducer needle from the patient's blood vessel, it is very important that the nurse is aware of the orientation of the bevel on the distal end of the introducer needle to ensure that the blood vessel is not pierced again or that the cannula itself is not pierced if the needle hub and cannula hub are inadvertently separated during the insertion procedure. Additionally, by placing the projection on the proximal end of the cannula member, it is often times difficult to secure the cannula member to the skin of the patient if the nurse desires to insert the catheter at a later time.
A number of prior assemblies are known to facilitate the separation of the needle hub from the cannula hub. These prior assemblies typically include the use of a projection extending from the proximal end of the cannula hub. The projection on the cannula hub facilitates the separation of the needle hub from the cannula hub by providing a surface on the cannula hub which may be pressed against while the needle hub is firmly held by the nurse. Although this projection makes the single handed separation of the needle hub from the cannula hub easier, it may also cause the needle hub to be inadvertently separated from the cannula hub during the insertion procedure.
Many of the prior assemblies use a friction fit between the interior of the cannula hub and the exterior of the needle hub as the primary method of retaining the needle hub in the cannula hub. When the needle hub is separated from the cannula hub to remove the introducer needle from the patient's blood vessel, the cannula hub is often rotated to release the frictional fit between the needle hub and the cannula hub. During this procedure, it is important that the bevel on the distal end of the introducer needle remain oriented in the same position as when the blood vessel was initially pierced so that the blood vessel is not pierced a second time by movement of the introducer needle in the patient's blood vessel as the needle hub and cannula hub are separated. Therefore, although it is important to have a secure connection between the needle hub and the cannula hub during the insertion procedure, it is equally important that the needle hub and cannula hub are readily separable when the introducer needle is to be removed from the patient's blood vessel. None of the presently available devices meet this requirement.
It is apparent that a need remains in the art for an over the needle catheter introducer which will secure the needle hub to the cannula hub while the assembly is introduced into the patient's blood vessel and will readily release the cannula hub from the needle hub when the introducer needle is removed from the patient's blood vessel.